Finding out you might have cancer is scary. One of the things doctors sometimes use to help figure out what’s going on are blood tests that look for “cancer markers.” But these tests aren’t like a simple yes/no answer. They’re more like clues in a puzzle, and it’s really important to understand what they can and can’t tell you.
This article will break down what cancer markers are, how reliable the tests are, and how they fit into the bigger picture of checking for cancer.
What Exactly Are Cancer Markers?
Think of cancer markers (sometimes called “tumor markers”) as signals. They’re substances, often proteins, that show up in your body. Sometimes, cancer cells themselves make these markers. Other times, your body makes them in response to cancer being there. You might find them in blood, urine, or even in samples of tissue.
The tricky part? Having a higher-than-normal level of a cancer marker doesn’t automatically mean you have cancer. And, just as important, having a normal level doesn’t guarantee you’re cancer-free. It’s more complicated than that.
Different Kinds of Markers
There are basically two main types:
- Markers made by the tumor: These are substances that come directly from the cancer cells. They can sometimes give an idea of how fast the cancer is growing.
- Markers made by the body: These are substances your body produces when it detects cancer. But – and this is important – your body can also make these markers for other reasons, even if you don’t have cancer.
A Look at Some Common Markers
Here’s a table showing some common cancer markers and the cancers they’re often associated with. But remember, this is just a general guide, and there’s a lot of overlap:
| Cancer Marker | Cancers It Might Be Linked To | Important Notes |
| PSA (Prostate-Specific Antigen) | Prostate Cancer | Can also be high if you have a non-cancerous prostate problem (like an enlarged prostate) or an infection. |
| CA-125 | Ovarian Cancer | Can also be high if you have endometriosis, pelvic infections, or even if you’re pregnant. |
| CEA (Carcinoembryonic Antigen) | Colorectal, Lung, Breast, and other cancers | Can also be high if you smoke or have inflammation in your bowels. |
| AFP (Alpha-fetoprotein) | Liver Cancer, Testicular Cancer | Can also be high during pregnancy or if you have certain liver diseases. |
| CA 19-9 | Pancreatic, Bile Duct, and Colorectal Cancer | Can also be high if you have pancreatitis or other digestive problems. |
| CA 15-3 / CA 27.29 | Breast Cancer | Mostly used to see how well treatment is working or if the cancer has come back. |
| HER2/neu | Breast Cancer, Stomach Cancer | This is a protein that helps cancer cells grow. Knowing if it’s there helps doctors choose the right treatment. |
| BRCA1 and BRCA2 | Breast, Ovarian, and other cancers | These are actually gene changes (mutations), not proteins. If you have these mutations, you’re at higher risk for certain cancers. Genetic testing is used to find them. |
| Calcitonin | Medullary Thyroid Cancer | Levels may also elevate due to conditions like renal failure. |
| Chromogranin A (CgA) | Neuroendocrine Tumors | Levels of Chromogranin A can also increase for individuals who are taking proton pump inhibitors. |
How Doctors Use Cancer Marker Tests
It’s important to know that doctors don’t usually use these tests to screen the general public for cancer. They’re more often used in these situations:
- Checking how well treatment is working: If someone has already been diagnosed with cancer, doctors can track the marker levels over time. If the levels go down, it often means the treatment is helping. If they go up, it might mean the cancer is growing or coming back.
- Looking for cancer that’s come back: After someone has been treated for cancer, regular marker tests can help catch it early if it returns.
- Understanding the likely outcome: Sometimes, the level of a marker can give doctors a clue about how the cancer might behave (this is called the prognosis).
- Helping with diagnosis (but not alone!): If a doctor already suspects cancer (because of other tests or symptoms), a high marker level might add to the evidence. But it’s never used as the only way to diagnose cancer. Regular Full Body Health Checkup can help in early diagnosis.
Are These Tests Reliable?
This is the most important thing to understand: cancer marker tests are not perfect. Here’s why:
- False alarms (False Positives): Many things besides cancer can make these markers go up. This can lead to worry, more tests, and sometimes even procedures that weren’t needed. For example, a simple prostate problem can raise PSA levels, and inflammation can raise CEA levels.
- Missed cancers (False Negatives): Some people with cancer might have normal marker levels. This is because not all cancers make these markers, and sometimes the levels aren’t high enough to be detected, especially early on. Relying only on a negative test could give a false sense of security. A Blood Test is essential for proper screening.
- Not specific enough: Many markers aren’t linked to just one type of cancer. For example, CEA can be high in several different cancers, and even in non-cancerous conditions. This makes it hard to know exactly what’s causing the high level.
- Everyone’s different: What’s considered a “normal” marker level can vary from person to person. Things like age, gender, and your overall health can affect the results.
Because of these issues, most medical groups don’t recommend routine cancer marker screening for everyone. The risk of unnecessary worry and procedures often outweighs the potential benefit.
When Might Screening Be Considered?
Even though these tests aren’t perfect, there are some situations where they might be helpful, usually for people at higher risk:
- Strong family history of cancer: If many people in your family have had a certain type of cancer (like breast cancer with BRCA1/2 gene changes), your doctor might suggest more frequent checkups, possibly including marker tests, along with things like mammograms or MRIs.
- Known gene changes: If you know you have a gene change that increases your cancer risk, your doctor might recommend specific screening, which could include marker tests.
- If you’ve had cancer before: People who have been treated for cancer are often monitored with marker tests to see if it comes back.
- A specific group who have symptoms may benifit from this test: If a doctor already suspects cancer (because of other tests or symptoms), a high marker level might add to the evidence. But it’s never used as the only way to diagnose cancer.
It’s All About the Big Picture
The key takeaway is that a cancer marker test result should never be looked at by itself. It must be considered along with:
- Your medical history: Your doctor needs to know about your past health problems and your family’s health history.
- A physical exam: A thorough checkup by a doctor is crucial.
- Other tests: This might include imaging tests (like X-rays, CT scans, MRIs, or ultrasounds), biopsies (taking a small sample of tissue), and other lab tests.
- Your symptoms: Anything you’re feeling that’s not normal is important information.
A doctor will put all these pieces of the puzzle together to figure out what a high or normal marker level means for you. They might recommend more tests, suggest waiting and watching, or refer you to a specialist.
What’s Next for Cancer Marker Testing?
Scientists are constantly working to find new and better cancer markers, and to make the existing tests more accurate. Some exciting areas of research include:
- “Liquid Biopsies”: These are tests that look at blood samples for things like cancer cells that have broken away from the tumor, pieces of the tumor’s DNA, and other clues. They hold promise for finding cancer earlier, choosing the best treatments, and seeing how well treatment is working.
- Studying proteins and genes: Advances in how we study proteins (proteomics) and genes (genomics) are helping us find new potential markers and understand how cancer works at a molecular level.
- Combining markers: Using several markers together in one test might make the testing more accurate.
- Home Testing: A Lab Test at Home is made possible for early detection of cancer using cancer markers.
These advances might eventually lead to better blood tests for finding and diagnosing cancer. But even with these improvements, marker tests will likely always be just one part of the overall approach to fighting cancer.
